CVSS CVSS Video Storage & Recording Systems 1 — Questions and Answers
Question 1: What is the primary functional difference between a DVR and an NVR in a surveillance system?
- DVRs support IP cameras; NVRs support only analog cameras
- DVRs process analog camera signals internally; NVRs record pre-encoded IP camera streams over a network (Correct answer)
- DVRs provide higher resolution than NVRs
- DVRs use cloud storage; NVRs use on-site hard drives
Correct answer: DVRs process analog camera signals internally; NVRs record pre-encoded IP camera streams over a network
A DVR encodes analog video signals itself, while an NVR records digital streams already encoded by IP cameras over a network connection.
Question 2: In RAID 5 storage used for video surveillance, what is the minimum number of drives required?
- 2
- 3 (Correct answer)
- 4
- 5
Correct answer: 3
RAID 5 requires a minimum of 3 drives to stripe data with distributed parity for fault tolerance.
Question 3: A surveillance system stores video at 4 Mbps per camera. How much storage (in GB) is needed for 1 camera over 24 hours?
- 28.8 GB
- 43.2 GB (Correct answer)
- 57.6 GB
- 86.4 GB
Correct answer: 43.2 GB
4 Mbps × 3600 sec/hr × 24 hr = 345,600 Mb ÷ 8 = 43,200 MB = 43.2 GB.
Question 4: Which video compression standard offers the best compression efficiency (smallest file size) at equivalent quality compared to H.264?
- MJPEG
- MPEG-2
- H.265 (HEVC) (Correct answer)
- H.261
Correct answer: H.265 (HEVC)
H.265/HEVC achieves approximately 50% better compression than H.264 at the same visual quality, significantly reducing storage and bandwidth requirements.
Question 5: What is the purpose of 'motion-based recording' in a video management system?
- Record video only when the camera detects pixel change, reducing storage consumption (Correct answer)
- Continuously record all cameras regardless of activity
- Trigger a PTZ camera to auto-track a moving subject
- Increase frame rate automatically when motion is detected
Correct answer: Record video only when the camera detects pixel change, reducing storage consumption
Motion-based recording saves storage by writing video only during activity, significantly reducing the total data recorded versus continuous recording.
Question 6: In surveillance storage planning, what does 'retention period' refer to?
- The time it takes to retrieve archived footage from cloud storage
- The number of days recorded video is kept before being overwritten (Correct answer)
- The maximum recording duration per camera per day
- The backup cycle interval for offsite storage
Correct answer: The number of days recorded video is kept before being overwritten
Retention period is the number of days video is stored before the oldest recordings are overwritten or deleted to free space.
CVSS CVSS Video Storage & Recording Systems 1
What is the primary functional difference between a DVR and an NVR in a surveillance system?